A convicted killer was found guilty Thursday of murdering a correctional officer at the now-closed Maryland House of Correction, opening the possibility that he will become the first person sentenced to death under the state's new capital punishment law.

The first-degree murder conviction of Lee Edward "Shy" Stephens came after almost six full days of deliberations by the jury of three men and nine women, who returned somberly to the Anne Arundel County courtroom where they had heard testimony for three weeks about the killing in 2006 of 42-year-old Cpl. David McGuinn.

Jurors and the five alternates will be in court again Monday morning. Stephens must decide if he wants them to sentence him or if he prefers to be sentenced by Circuit Judge Paul A. Hackner. Hackner will preside over hearings that will determine whether the 32-year-old prisoner, who is already serving a sentence of life plus additional years, receives a death sentence.

Members of the victim's family sat motionless as the verdict was read, some with tears in their eyes. They hugged prosecutors as the packed courtroom began to empty.

Stephens turned to look at his family after the verdict was read. They shook their heads.

The families filed silently out of the courtroom with the lawyers. Participants in the case remain under a gag order.

The state Department of Public Safety and Correctional Services said in a prepared statement that "Officer McGuinn's dedication to Maryland won't be forgotten. Our thoughts are always with his family."

The verdict brought a sense of satisfaction to correctional officers' union leaders.

"We are relieved that justice has finally been served, after almost six years now," said Patrick Moran, director of AFSCME Maryland, a collective-bargaining unit for correctional officers. "There was no doubt in anyone's mind he was going to be found guilty."

The verdict came a day after the state Board of Public Works gave the go-ahead for most of the antiquated House of Correction, shut in the wake of McGuinn's death and other violence, to be dismantled rather than razed. The less costly technique involves more recycling.

Stephens was convicted in the fatal stabbing July 25, 2006, of the two-year veteran of the Department of Correction, who was nicknamed "Homeland Security" for his no-nonsense approach to the job. McGuinn was killed as he conducted the 10 p.m. prisoner head count. Anne Arundel County prosecutors maintained that two prisoners ambushed and killed him after they escaped from cells that were supposed to have been locked.

Not only did other prisoners on the tier know the attack was coming, but many used mirrors to watch from their cells, according to a prisoner who testified for the prosecution and identified Stephens and another prisoner as the killers.

A 2009 law limits capital punishment to murders in which there is DNA or other biological evidence that links the defendant to the murder, a videotaped confession or a video recording of the crime. McGuinn's blood was on Stephens' clothing, his shoes and in his cell, as well as on a T-shirt that prosecutors suspected Stephens wound around his hand to hold the weapon.

Investigators found hundreds of homemade weapons and other contraband in the aftermath of the killing at the troubled prison — but no murder weapon.

Stephens and another convicted murderer, Lamar (also spelled Lamarr) Cornelius "Junebug" Harris, 41, trapped McGuinn as he strode the catwalk lined with about 50 cells in the maximum-security facility in Jessup, prosecutor Sandra F. Howell told the jury during closing remarks last Wednesday.

Defense lawyer Michel E. Lawlor argued that the crime scene was too bloody and the evidence from Stephens' cell was contaminated. Seven prisoners were called as defense witnesses, telling jurors that two large masked men attacked McGuinn, but they didn't know who they were.

Lawlor said that the state's star witness, a fellow prisoner, couldn't have seen the assault on McGuinn well enough to identify the attackers because he was too far away and lighting was dim. He also said the witness didn't come forward until he was facing a 22-year sentence on federal charges.

Harris is also serving a sentence of life plus additional years. Whether he will be tried is unclear. A hearing on whether he is mentally competent to stand trial has been scheduled for April.

During the summer that McGuinn was killed, three prisoners died in inmate-on-inmate attacks. In early March 2007, another correctional officer was stabbed; he survived.

Two weeks after the second correctional officer was stabbed, the prison was emptied and shut down. State officials said that the structure, built in 1879, couldn't be made safe.